Seal Bore for High Expansion Bridge Plugs

ABSTRACT

One or more pup joints are provided in a tubular string at one or more predetermined locations. The seal bores are recessed to protect them from passing tool until needed as a sealing location for a packer or bridge plug having a metal-to-metal seal that is radially extended into sealing contact with the seal bore surface. The seal surface can be recessed to protect it from passing tools. A coating or sleeve can be fit to the sealing surface that is penetrated by the sealing element of the packer or bridge plug for the metal to metal seal. The presence of the protective sleeve can also enhance the metal to metal seal by abutting the sealing element on opposed sides after the sealing element penetrates through the sleeve.

FIELD OF THE INVENTION

The field of this invention is packers or bridge plugs that use ametal-to-metal seal and more particularly seal bore sections inserted ina tubular string in which such packers or bridge plugs are set.

BACKGROUND OF THE INVENTION

Packers and bridge plugs are barrier devices to isolate zones in aborehole for a variety of purposes. Historically these devices havefeatured one or more resilient sealing members that were squeezedtogether longitudinally to increase their diameter to seal off anannular space around the packer or plug. Such devices could bemechanically set with setting tools or could be hydraulically set with aball dropped on a seat followed by pressuring up the tubing. Typicallythe set position would be retained with slips that engaged the tubularwall on one or both sides of the sealing element.

While such designs have been used for decades, they have limitationswhen there are high differential pressures or high service temperatures.The resilient material for the seals generally has an upper temperaturelimit of about 350 degrees F. To make up for these limitations andlimitations on the degree of expansion of the traditional mechanicallyset compressible elements, new designs have been developed that use ametal to metal seal such as by collapsing a pre-scored tube so that itfolds along the scores and extends outwardly. Such a metal to metal sealdesign is described in U.S. Pat. No. 7,134,506. Other metal seal designsare described in U.S. Pat. Nos. 7,448,445; 7,165,622; 6,962,206 and5,685,369. Such packers or bridge plugs are also the subject oftechnical articles such as: Wellbore Isolation Intervention DevicesUtilizing a Metal-to-Metal Rather Than an Elastomeric SealingMethodology Gordon Mackenzie and Garry Garfield, Baker Oil Tools SPE109791-MS 2007; Recent Metal-To-Metal Sealing Technology for ZonalIsolation Applications Demonstrates Potential for Use in Hostile HPHTEnvironments Garry Garfield and Gordon Mackenzie, Baker Oil Tools SPE105854-MS 2007; Metal-to-Metal Sealing Technology: Bridging the GapBetween Conventional and High-Expansion Zonal Isolation Applications SPEGarry Garfield and Gordon Mackenzie, Baker Oil Tools SPE 107107-MS 2007and Wireline Deployed Metal Sealing Bridge Plug System: OperationalLearning Curve and Subsequent Redevelopment I. C. Chapman, SPE, K. S.Ng, SPE, ExxonMobil Development Company; N. M. Nor, SPE, RasGas CompanyLimited; G. R. J. Mackenzie, SPE, G. L. Garfield, SPE, Baker Oil ToolsSPE 113891-MS 2008.

The issue that has developed with metal-to-metal high expansion plugs iswhen they are set in API tubulars whose inner wall condition canundermine the sealing contact with the element. The tubular can havesome degree of out of roundness or simply an uneven surface fromexternal loads that have caused a part of the circumference to dentinwardly. There can be scale added to the inner surface or corrosionthat takes away some of the wall surface. Scoring can occur fromwireline damage or even a drilling assembly passing through the sealbore. In short, the tubular at the location where the metal seal is tobe actuated is not ideal for a seal of the desired level or in somecases any seal at all.

The present invention addresses this issue by placing at strategiclocations seal bores that have been machined and polished to requiredtolerances that when the metal seal is extended into contact with theseal bore, a seal to the required specification is accomplished. Theseal bore can have an optional coating and can further be optionallyrecessed in a pup joint to further protect it until use. The sealingelement will merely penetrate the coating to make sealing contact withthe seal bore wall. These seal bores can be located by counting adistance from a predetermined number of casing collars for example orother location techniques can be used. An optional possibility is to uselanding shoulders or some other internal tubular condition that makesthe packer or bridge plug stop at the location where its sealing elementwill be in the seal bore. Alternatively a radioactive source can beplaced in or near the seal bore whose presence can be detected by thepacker or bridge plug as it is advanced in the bore.

While seal bores have been in use before, the application has been toinsert an object with external ring seals into the seal bore in aninterference fit to obtain sealing contact. A few examples of such sealbores are shown in U.S. Pat. Nos. 4,612,985; 4,443,726 and 4,111,435.The present invention associates a metal to metal seal or a non-metallicseal or a non-elastomeric seal with a seal bore with the option ofprotecting the polished surface having a predetermined diameter so thatsealing integrity can be attained in the desired location or locations.Those skilled in the art will further appreciate other aspects of thepresent invention from the detailed description of the preferredembodiment and the associated drawings while recognizing that the fullscope of the invention is to be determined by the appended claims.

SUMMARY OF THE INVENTION

One or more pup joints are provided in a tubular string at one or morepredetermined locations. The seal bores are recessed to protect themfrom passing tool until needed as a sealing location for a packer orbridge plug having a metal-to-metal seal that is radially extended intosealing contact with the seal bore surface. The seal surface can berecessed to protect it from passing tools. A coating or sleeve can befit to the sealing surface that is penetrated by the sealing element ofthe packer or bridge plug for the metal to metal seal. The presence ofthe protective sleeve can also enhance the metal to metal seal byabutting the sealing element on opposed sides after the sealing elementpenetrates through the sleeve.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a bridge plug set in a seal bore;

FIG. 2 shows as seal bore in a tubular string; and

FIG. 3 is an enlarged view of the seal bore joint shown in FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring first to FIG. 2 there is a tubing string 10 that has periodiccouplings 12 and 14. In between is a shorted section or pup joint 16that has an interior dimension 18 that is recessed between ends 20 and22 so as to protect the surface 18 that is preferably polished to apredetermined tolerance while holding a dimension within a closetolerance as well. While a single joint 16 is illustrated those skilledin the art will appreciate that a plurality of such joints 16 can bepart of a string 10. The joints 16 with their interior dimension orsurface 18 are the seal bores 24 where a packer 26 that features a metalto metal seal 28 that when set will penetrate the surface 18. As anoption there can be a coating 30 that is in the form of a sleeve thatcan be snapped into position such as when it has a longitudinal split.Alternatively strips of soft material can be used if retained to eachother or to the surface 18 with adhesives. The objective of theprotection 30 is to prevent damage to the surface 18 when tools are runthrough it before a packer or bridge plug 26 is placed into positionwith a metal to metal seal against surface 18. Having the surface 18recessed between ends 20 and 22 is another way to protect the surface 18from tools that pass by. Optionally both these features can be usedtogether in a given seal bore assembly 24. As another option the coatingor cover 30 can be a soft metal compatible with well fluids or plasticor a composite. The material can be fairly thick in the order of 6 cmand the metal ridges 32 and 34 will go right through it as shown inFIG. 1. The fact that the sleeve continues to abut the metal ridges 32and 34 after they penetrate the sleeve or coating 30 will enhance theseal. Clearly to realize this effect a continuous sleeve 18 should beused in the thickness range mentioned. A preferred material is PTFEotherwise known as Teflon®. The preferred way of applying this “sleeve”is to spray the Teflon directly onto the heated surface. A uniform layer0.030″ thick can be built up with this process.

Those skilled in the art will appreciate that seal bores 24 can beplaced between zones based on available well data for where in thefuture isolation may be needed. By actuating metal to metal packers orbridge plugs 26 so that they engage a seal bore 24 having a surface 18of a known dimension within narrow tolerances and the requisite surfacesmoothness or level of polish, the performance of the packer or plug 26in getting a seal of the required degree will be more likely and theuncertainties of API tubulars that have been in service for a long timeand have issues of out of roundness, corrosion, or scale buildup will beeliminated. With the use of a coating or cover 30 that is compatiblewith well fluids, even long term exposure downhole should not change thedimensional and polish characteristics of the seal bore 24 at itssurface 18.

Recessing the surface 18 with respect to ends 20 and 22 will protectsurface 18 with or without a coating or sleeve 30. The coating or sleeveor other protective shape 30 can be left in place and penetrated asshown in FIG. 1 or alternatively it can be removed, preferablychemically by spotting a material adjacent the sleeve or sleeves 30 anddissolving, or melting with heat or in some other way causing aseparation of the protective member 30 from the adjacent surface 18.Optionally, recesses or other locating devices 36 or 38 can be placedabove or below the surface 18 to aid in the location of a packer or plug26 at the desired seal bore 24. The locating devices can be configureddifferently for each plug or packer 26 so that a matching configuration(not shown) on the plug or packer 26 will endure that only the desiredlocation will stop the plug or packer for setting at the desired sealbore 24.

The metal to metal packer or plug 24 are of a type known in the art anddescribed in some of the cited art above such as U.S. Pat. No.7,134,506. However, with the use of seal bores 24 having a surface 18 ofa known dimension, prior designs of packers or plugs 26 can be designedto be set in a specific bore dimension as opposed to the currentpractice where a given packer or plug 26 is designed for a range ofdiameters to handle for example different wall thicknesses for a givensize of tubular, with the seal nearer the larger dimension of the rangeseeing a smaller retained force to hold the metal to metal seal.Instead, with a known seal bore 24 the plug or packer can be optimizedto a specific sealing dimension whose integrity will remain at the timethe packer or plug 26 is finally run in for zonal isolation.

The above description is illustrative of the preferred embodiment andmany modifications may be made by those skilled in the art withoutdeparting from the invention whose scope is to be determined from theliteral and equivalent scope of the claims below.

1. A method of subterranean zonal isolation, comprising: providing at least one seal bore assembly of a predetermined diameter in a tubular string; running in at least one barrier having an extendable seal to said seal bore assembly; actuating said metal seal into metal to metal sealing contact with said seal bore assembly.
 2. The method of claim 1, comprising: providing a sealing surface having said predetermined diameter on said seal bore assembly; positioning at least one end portion adjacent said sealing surface with a smaller diameter than said sealing surface.
 3. The method of claim 1, comprising: providing a sealing surface having said predetermined diameter on said seal bore assembly; covering said sealing surface with a cover.
 4. The method of claim 3, comprising: making said extendable seal metallic; penetrating said cover while extending said metal seal.
 5. The method of claim 4, comprising: using said cover to aid the seal formed by said metal seal.
 6. The method of claim 4, comprising: penetrating said sealing surface with said metal seal.
 7. The method of claim 3, comprising: making said extendable seal metallic; removing said cover before actuating said metal seal.
 8. The method of claim 2, comprising: positioning two end portions on opposed sides of said sealing surface so as to recess said sealing surface with respect to said end portions.
 9. The method of claim 1, comprising: making said extendable seal metallic; providing a locating device on said seal bore assembly to engage said barrier for locating said metal seal with respect to said seal bore assembly.
 10. The method of claim 1, comprising: fully covering said sealing surface with said cover.
 11. The method of claim 10, comprising: building said cover onto said sealing surface or forming said cover into a sleeve and inserting said sleeve against said sealing surface.
 12. The method of claim 9, comprising: providing discretely shaped locating devices on different seal bore assemblies on said tubular string; matching a mating device on said barrier so that it locates at a single predetermined location.
 13. The method of claim 1, comprising: providing a plurality of spaced seal bore assemblies on said string; locating said at least one barrier on at least one predetermined seal bore assembly.
 14. The method of claim 1, comprising: making said extendable seal metallic; configuring said metallic seal to specifically engage the predetermined dimension of said sealing surface as opposed to the variations of inside diameter of said string size taking into account the variety of wall thickness sizes that could be used for said string.
 15. In combination at least one barrier for a metallic tubular string having an extendable seal and at least one seal bore as a component of said string against which said extendable seal selectively engages for a seal.
 16. The combination of claim 15, wherein: said seal bore comprises a joint in said string and a recessed sealing surface between ends of said joint.
 17. The combination of claim 15, wherein: said seal bore comprises a joint in said string and a sealing surface that is covered.
 18. The combination of claim 17, wherein: said seal is metallic and penetrates said cover when extended.
 19. The combination of claim 18, wherein: said extendable metallic seal penetrates said sealing surface.
 20. The combination of claim 18, wherein: said penetrated cover cooperates for sealing with said extendable metal seal.
 21. The combination of claim 15, wherein: said seal bore comprises a joint in said string and a sealing surface of a predetermined diameter; said extendable seal is metallic and configured to sealingly extend specifically for sealing against that predetermined sealing surface diameter instead of a variation of internal tubular diameters possible for a string of a given size taking into account the variation in wall thickness for different weights per foot.
 22. The combination of claim 17, wherein: said sealing surface is fully covered by a sleeve or by a cover built on said sealing surface. 